Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $193.26   11.222%   $214.9476   $214.95   $214.95   $214.90  
  Purchase #2 $64.50   13.374%   $73.1262   $73.13   $73.15   $73.10  
  Purchase #3 $147.89   9.193%   $161.4855   $161.49   $161.50   $161.50  
  Purchase #4 $39.40   13.797%   $44.836   $44.84   $44.85   $44.80  
  Purchase #5 $11.55   6.727%   $12.327   $12.33   $12.35   $12.30  
  Purchase #6 $207.45   7.716%   $223.4568   $223.46   $223.45   $223.50  
  Purchase #7 $37.40   12.729%   $42.1606   $42.16   $42.15   $42.20  
  7 purchase totals = $701.45       $772.3397   $772.36   $772.40   $772.30